Cell separation processes
Plants continuously produce new organs during their life cycle, and they are provided with cell separation mechanisms whereby entire leaves, flowers, seeds or fruits, are detached from the plant.
We are studying floral organ abscission using the mutant inflorescence deficient in abscission, ida.
Premature shedding of flowers, seeds and fruits results significantly reduced yields (5-20%) in important crops (e.g. oilseed rape); flower and petal abscission reduces the sales value in ornamentals. Thus the understanding of cell separation processes is important for competitive horticulture, and for sustainable agriculture that makes optimal use of the arable land available for food and feed production.
IDA encodes a small protein with a N-terminal secretory signal peptide. Arabidopsis plants with mutation in the IDA gene retain their floral organs indefinitely, while overexpression of IDA induces earlier abscission, as well as ectopic shedding of whole flowers, cauline leaves and branches, organs that normally do not abscise in Arabidopsis.
This overexpression phenotype is dependent on the leucine-rich-repeat receptor-like kinases (LRR-RLKs) HAESA (HAE) and HAESA-LIKE2 (HSL2) HAE and HSL2 genes, and is not found in hae hsl2 mutant background, consistent with IDA being the ligand of these receptors.
The active part of IDA is confined within a peptide (EPIP) of 20 amino acids in the C-terminal end. this C-terminal motif is conserved in protein encoded by IDL genes. IDL genes are expressied at sites were cell separation events occur suggesting that IDL peptides also may be involved in cell separation processes. We are presently identifying the receptors of the IDL peptides and elucidating their function.
Our studies on floral abscission are funded by the Reseach Council of Norway.